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Technical data are subject to change without notice.
ISO 9001 certified. © Copyright SPM 1998-6. 71416.B
SPM Instrument AB • Box 4 • S-645 21 Strängnäs • Sweden
Tel +46 152 22500 • Fax +46 152 15075 • info@spminstrument.se • www.spminstrument.se
Fault Analysis Chart
Record results.
Measure again
according to
schedule.
Recent maintenance, machine off load or stopped.
Measuring fault.
Something broken, loose, or missing.
Measure Vibration Severity
One step on the chart below (any class at any
level) represents a 1.6 times increase from
previous value.
Each condition band (= 2 steps) represents a
2.5 times increase, i.e. a significant change in
vibration severity.
3 steps up is a fourfold increase, an alarming
change demanding immediate action.
Class Class Class Class Class Class
RMS
mm/s
Limits
1 step
Time Schedule Machine Class Measuring Point
No
change
Change
?
Decrease
Increase
< 1 step
Mainly
radial
Treat large unexplained decrease like large
increase. Investigate soonest.
Plan to maintain
when vibration
increases 2 steps
above new or
good level.
Slow build-up of
dirt.
Steady wear,
corrosion.
Stretched or
slipping belts.
Axial
+ radial
Slack mounting bolts,
loose frame parts,
etc.
Coupling wearing or
stiffening.
Gear tooth wear.
Direc-
tion
?
How
much
?
> 1 step
Where
?
Part of
machine
All over
machine
Mainly radial: Failed fan
blades, loss of balance
weights, shedding of dirt.
Oil film hysteresis whirls,
excessive bearing play.
Radial and axial: Changes in
foundation or support
structure causing serious
misalignment or looseness.
Bent or fractured shafts.
Critical speed and other
resonances.
Small machines: Possibly
transmitted vibration from
larger machines.
Radial and axial:
Slack or sheared
mounting bolts.
Damaged machine
feet, bent or
damaged subframes
or supports.
Faulty alignment,
bent or cracked
shaft.
Gear tooth damage.
Vibration up 2 steps from original or good level:
Plan to maintain, measure more frequently.
Vibration up 3 steps:
Inspect and maintain as soon as possible,
measure daily.
Vibration up 4 steps or more:
Shut down immediately and investigate.
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